Money market accounts are mutual funds for holding cash. Because they’re designed to be low-risk, many investors have come to think of them much like savings accounts, although the lack the federal deposit insurance guarantee of conventional bank accounts.

The funds are liquid, which means investors can withdraw their money quickly, much like a bank account. The fear is that some new economic panic — an escalation of the European debt crisis, for example — might prompt a run on funds that would set off a chain reaction. The funds are key source of capital for short-term credit markets that many companies and governments rely on to fund daily operations.

Here’s what’s Schapiro is proposing to strengthen the funds, according to the New York Times:

The proposed changes include requiring money market funds to use floating net asset values to report their performance, rather than the fixed $1 a share that they use now, or to require the funds to maintain a capital buffer to stabilize their values. Also being considered are restrictions or fees on investor withdrawals.

So far, Schapiro hasn’t been able to convince a majority of the SEC’s commissioners. Three of the five oppose any additional restrictions. So does the mutual fund industry, of course, fearing that it will scare many investors away from money funds entirely.

Certainly, imposing fees for withdrawing your own money from your account would make many people think twice about where they park their cash. While money market funds certainly aren’t risk-free, as the new study shows, they also bear less risk than many other investments. Once again, it seems, the cost of stabilizing the financial system comes at the expense of savers: retirees and others who are trying to be careful with their money.